Sunday, April 29, 2007

Accessing Exchange 2007 Unified Messaging: Part 2 - Implementation Plan

All successful projects need to start with a plan...

Extension Pools
Firstly, we need to determine how many digits are in our internal extensions. We will use a 3 digit extension code in this guide, but feel free to increase it to as many as you need. We will break up our extensions into the following ranges, for ease of routing:
  • 2xx – Extensions handed by the Exchange Server. Used for auto attendants and subscriber access.
  • 3xx – Extensions handled by the sipX server. We will only use these for testing and troubleshooting.
  • 4xx – 5xx – Extensions handled by Asterisk. This is our usable pool that end users will be assigned extensions from.
I purposely excluded the ranges 0xx, 1xx and 9xx so as not to conflict with emergency numbers in various locations (000, 112, 911), other than that, there are no restrictions on what extension ranges you use.

IP Addresses and Hostnames
The following IP addresses and hostnames are in use on my network. Substitute your own addresses as appropriate throughout this guide.




sipX server


Asterisk/Trixbox server


Exchange server


You must configure the appropriate DNS host (A) records as shown above. The use of host files is not supported in this guide. If you are using host files, and run into problems, the first thing I am going to tell you to do is configure DNS.

PLEASE NOTE: sipX is VERY picky when it comes to name resolution. If you have configured sipX to be responsible for SIP traffic coming to, it will not correctly handle SIP traffic addressed to sipX.lithnet.local, even through the domain name translates to the correct IP address. I will cover this later in more detail, but at this stage, just make sure that the same hostname resolves to the same IP address on each server.

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